In November, one of the largest and most rigorous trials of
the vitamin ever conducted — in which 25,871 participants
received high doses for five years — found no impact on cancer,
heart disease, or stroke.
How did we get it so wrong? How could people with low vitamin D
levels clearly suffer higher rates of so many diseases and yet not
be helped by supplementation?
As it turns out, a rogue band of researchers has had an
explanation all along. And if they’re right, it means that once
again we have been epically misled.
These rebels argue that what made the people with high vitamin D
levels so healthy was not the vitamin itself. That was just a
marker. Their vitamin D levels were high because they were getting
plenty of exposure to the thing that was really responsible for
their good health — that big orange ball shining down from above.
The oldest mistake in the book: conflating cause and effect (or, if you prefer, correlation with causation). In addition to vitamin D supplements being useless, the flip side of this argument is that sunscreen is generally doing us more harm than good — that the benefits of exposure to sunlight far outweigh the increased risk of skin cancer.